Electric connecter



Dec. 28, 1937. J, oBERMAlER Y 2,103,548

ELECTRIC CONNECTER Original Filed Oct. 1, 1954 1N VENTQR. Jofiiz 4.06627724162 MW ATTORNEY.

Patented Dec. 28, 1937 PATENT OFFICE ELECTRIC CONN ECTER John A.Obermaier, Chicago, Ill.

A plication October 1,

'1934, Serial No. 746,379

Renewed November 5, 1937 3 Claims.

This invention relates to electric connecters in general, and moreparticularly to the plug and socket type of connecter, although notlimited thereto.

It is one of the objects of the present invention to provide a plug andsocket connecter of the two or three prong type which is particularlyadapted for use in a circuit for the electrical measurement oftemperature. Consider a usual type of electric resistance temperaturemeasuring system. A thermo-resistance element is connected by a plug andsocket connecter in a circuit that includes means for measuring itsresistance, or change in resistance, which varies as a known function ofthe temperature. The measuring apparatus may be calibrated to give thetemperature directly, or the temperature can be determined indirectly,from the resistance. The measuring apparatus really measures the currentthat flows through the circuit upon the application of a predeterminedpotential thereto, the resistance being then taken as a predeterminedfunction of the current. This is true only if there are no extraneoussources of potential in the circuit modifying the current fiow. I havediscovered that the connection between the thermo-resistance element andthe rest of the circuit constitute a possible source for the generationof an extraneous thermo-electric potential which might seriously affectthe accuracy of the measurement. It is one of the objects of the presentinvention to provide a plug and socket type of connecter which willeliminate, or substantially reduce, this source of error. The lineconductors extending to the terminals of the connecter are of adifferent material than the connecter itself, hence a thermo-electric E.M. F. will be set up whenever a temperature difference exists betweenthe terminals. I eliminate, or substantially reduce, the'possibilitiesof the establishment of such temperature difference and thus avoid thissource of error. I do this by making the connecter of a minimum outsidediameter, thus reducing, as far as possible, the establishment of atemperature difference between different parts of the connecter, and Imake the terminals themselves as large as possible, within the smalldiameter available.

It is a further object of the present invention to provide a terminalfor receiving a conductor and firmly clamping the same in place, whichis simple and economical in construction and wherein the conductor isfirmly wedged in place against becoming loosened by vibration.

It is a further object of the present invention (Cl. 17336l) to providea terminal structure wherein the conductor is wedged in place by asingle screw and wherein the conductor serves in the manner of a locknut to lock the screw against becoming loosened by vibration.

The attainment of the above and further objects of the present inventionwill be apparent from the following specification taken in conjunctionwith the accompanying drawing forming a part thereof.

In the drawing:

Figure 1 is a view, in partial longitudinal section, of a resistancethermometer bulb having my improved connecter structure, the cap beingseparated from the rest of the unit to facilitate illustration;

Figure 2 is a view taken along the line 2-2 of Figure 1;

Figure 3 is a fragmentary view illustrating the plug and socket in theirconnected position;-

Figure 4 is an enlarged view of the male connecter terminal, withthe-holding screw removed;

Figure 5 is a sectional view taken along the line 5-5 of Figure 4, withthe holding screw in position;

Figure 6 shows a modified form of terminal;

Figure 7 shows a modified form of wire holding means in a male connecterterminal;

Figure 8 is a sectional view taken along the line 88 of Figure '7;

Figure -9 is a view of a connecter plug with a compensating resistancemounted thereon;

Figure 10 is an end view thereof; and

Figure 11 is a top view of the socket for the plug of Figure 9.

Reference may now be had more particularly to Figures 1 and 2 of thedrawing. A resistance thermometer bulb is indicated at I, terminating ina head or terminal support 2 having a pair of socket terminals 3-4 and acompensating re- .sistor 5. The resistance thermometer bulb is of aconstruction such as is shown and claimed more particularly in mypending application Serial #741,286, filed August 24, 1934, and, exceptin combination with the jack structure to be presently described, formsno part of the present invention.

The jack structure comprises a pair of male terminal plugs 8 and 9 thatcooperate with the socket terminals 3 and t. The plugs are riveted on adisc E0 of suitable insulation, such as the material known as Bakelite.The disc 80 is provided with an opening it which receives a projectingportion H of the compensating resistor 5. When the plug is fullyinserted into the till socket, a shoulder 63 on the resistor l bearsagainst the disc It. The circuit to the plugs 8 and 9 is extended bywires H of a two wire conductor l which extends through a cap it, arubber gasket H, a pair of flat metal washers l8,

a metal thimble l9 and a gasket 20 in the form of a piece of rubbertubing. The lower end of the thimble I9 is outwardly flared afterinsertion into the cap it, the flared portion 2! extending loosely intoa peripheral groove 22 in the cap. This prevents withdrawal of thethimble but allows a limited longitudinal and free rotational movementof the thimble with respect to the cap. The thimble thus retains thegasket H and the washers l 8 in the correct order as inserted in thefactory, while the terminal structure is being connected to theconductor 85 on the job. The conductor to is slidable through the tubing2 so that by pushing downwardly on the conductor it the jack structuremay be pushed forward to facilitate insertion of the male terminal plugs8 and 9 into the sockets 3 and 41. There after the cap it is sliddownwardly and threaded on the threads of the head or terminal supportEl. This serves to compress the rubber gasket 5 and the rubber tube to.Compression of the gasket ill seals against the entrance of moisture orother impurities, by Way of the opening 26 thence by way of the innersurface of the cap it and between the cap and the thimble it to theconnecter. Axial compression of the rubber tube 2t causes it to expandradially into firm engagement with the conductor i5 and thus sealagainst the entrance oi moisture, or other impurities, to the terminalstructure by creepage along the surface of the conductor The discs it?serve as 'slip triction members between the gasket it, which rotateswith the cap, and the thimlole, which does not rotate.

The tuloe 263 and the thlmlole i do not ro-= tate respect to theterminal structure the cap is advanced on the threads of the head 2,since coeficient of friction. between the thimhle l9 and the tuhe to isfar greater than that between the thimlole and the cap The compressionon the tube 2@ is compression and ere is no tendency for the tube, gripping so conductor 55, to twist the same. This tance not only while thecap is heing owned on the head 2, hut also when it he. away from thehead 2. "When tubing to has been. compressed to conductor :15 for aconsiderable length oi time there is a tendency, under somecircumstances, for the rubber tube as and the rubberized covering on theconductor l to he= oorne sweated together as if welded. my turniorceapplied to the tube so while it is still compressed the conductor maytwist outer covering of the conductor iii and cause irreparable injuryto the conductor insulation. lily my arrangement, whereby all twistingis avoided, the compression between the tubing and the conductor i6 isreleased before they are moved any appreciable amount with respect toone another. Even then, if the tube and the conductor to adhere to oneanother, they do not have to he separated insofar as concerns the estahllshment or disestahlishment of the electrical connections.

it is to he noted that the opening in the rubber gasket it is sumcientlylarge to prevent engage went oi the gasket with the conductor I15 evenwhen the gasket is compressed,

A gasket 27? may, ii desired, he pro vided to help seal the jointbetween the cap 16 and the head 2 when the cap is threaded on the head.I

. A description will now be given of the construction of the plugterminal 8 for which reference may be had to Figures 4 and 5. Theterminal comprises a metal body portion 30 from which extends anintegral stem 3| that forms a rivet for mounting the terminal, and anintegral plug portion 32 slitted at 33 to give it resiliency. The bodyportion 3 has a hole 34 formed therein and tapped and threaded toreceive a screw 35, and has an enlarged cylindrical bore 36 forreceiving the head 3?! of the screw. A conductor receiving hole orgroove 38 is formed through the body portion to adjacent to but spacedfrom the hole to. The bared end oi the conductor it extends through ahole till in the disc it in alignment With the hole 38 in the connecterterminal. The hole 38 intersects the enlarged bore 36. The exposedportion of the hole 3t constitutes a groove in which lies a portion ofthe conductor it, exposed as indicated at 32, and

extending above the surface 53 that constitutes the bottom of the bore3%. As the screw to is threaded into the opening 341 the bottom of thehead 371 of the screw ultimately engages the portion 4%? of theconductor. Further advancement of the screw causes it to compress theconductor and wedge it into high pressure engagement with the terminal.At this time the head of the screw is guided in the bore 35. At the sametime, since the conductor presses upwardly against only the left side ofthe screw head, as seen in Figure 5, and also tends to push the head ofthe screw to the left, the shank of the screw becomes tightened, thesame as if a lock nut or lools washer were used. In effect, theconductor acts somewhat as would a lock Washer to lock the screw againstbecoming loosened by vibration, but more effectively, since theconductor acts on only one side of the screw rather than uniformlyaround it. The natural elasticity of the conductor metal causes it toresist distortion, and when it is distorted to exert a force tending torestore it to its original shape. This force is exerted against the headof the screw and tends to hold the screw against becoming loosened.

The screw is a right hand screw. Since the conductor enters opening fromthe lower left side, as seen in Figure 4, tightening of the screw willtend to draw the condoctor further into the opening 38, rather than toforce it outwardly.

It is to he noted that the body" portions of the two terminals closetogether, thus making the outside ieter of the jack quite small. in"body portions are rather massive, for e s ace available. "5y rea son oftwo I reduce to a minimum the possihz'dity for the establishment of atemperature difference hetween two terminals and us practically elimi.ate the lilzeiihocd oi the establishment at terminal structure.

in Figure d, l have shown my invention applied to connecter terminalwhich is not oi the plug and socket in this case the connecter isprovide-cl with two openings and 38', one for receiving a conductor andthe other for r ceiving a conductor 655". by its own screw or in thesome manner as it conductor M in the connecter terminal of Eachconductor is held Figures e ti. thus apparent that my th W vention isnot limited to a connecter of the plug and socket type.

In Figures"? and 8 I have shown still another form of connecterterminal. This terminal consists of a solid block of metal, indicated at50, from which extend two rivet studs 5l-52 formed integrally therewith,and a male contact plug 53. that is also vformed integrally therewithand corresponds to the plug 32. On the front face of this terminal thereis formed a groove 54 that corresponds to the hole or groove 38. Theconductor I 4 lies in this groove and extends beyond the surface of theblock 50, above, as seen in Figure 8. A pair of spring metal plates55-55 are laid over the conductor and each secured in place by a pair ofscrews 565'6. The plates 55 press down upon the conductor and force itinto high pressure engagement with the block 50. At .the same time theconductor l4 exerts an upward force on the plates, which force istransmitted to the screws 56 more at the centrally innermost part of thescrew head than at the outer portion,

due to the bulge 51 in the portion of the plate immediately over theconductor. This force tends to lock the screws against becoming loosenedby vibration.

In Figures 9, 10 and 11 I have shown a modification of the plug andsocket terminal connecter, in that here the compensating resistor ismounted on the plug structure instead of adjacent the sockets 34 of theterminal head 2'; In this construction the terminal head is providedwith the two sockets 3 and 4, the .same as in the structure of Figure 1,and with a third socket 65 in lieu of the compensating resistor 5. The

I three conductors, indicated at 6, are connected,

respectively, to the three sockets. The plug terminal includes two maleplugs 8 and 9, as in Figure 1, and a third male plug l l' at the end ofa compensating resistance 5. The -compensating resistance 5' is mountedon the disc in any desired manner. One of the conductors I4 is con-,nected directly to the plug 8. The other conductor is connected to theplug H in series with the compensating resistance 5. The third plug 9 isa dummy plug and makes contact with a dummy socket 4. During calibrationof the line 315 leading to the plug connecter, the conductor that isnormally to be connected to the plug 8 is connected to the plug 9, andadjustment of the compensating resistance 5' to compensate for theresistance of the internal leads within the thermoresistance bulb I ismade as is pointed out more fully in my pending application abovereferred to. If desired, a fibre or other insulating disc 68 is strungover the plugs 8-,'9 and I0, and serves to brace them against inward oroutward separation.

It is to be noted that the socket 65 is of a shape specificallydiiferent from that of the other two sockets. This serves to polarizethe plug and socket assembly and prevent joining of the plug and socketin incorrect relationship of the plugs with the sockets. The two can bebrought together only when the plugs 8, 9 and II are over the sockets 3,4 and 55, respectively. of course, other polarizing arrangements mightbe used.

In compliance with the requirements of the patent statutes I have shownand described a few preferred embodiments of my invention. It is,however, to be understood that the inventionis not limited to theprecise structures shown, the same being merely illustrative. What Iconsider new and desire to secure by Letters Patent is:

1. An electrical connecter comprising a disc of insulation, a block ofmetal having at one end a riveting stem extending through an opening inthe disc and riveted over to secure the block to the disc, the oppositeend of the block having a male type connecter prong extending therefrom,said block of metal having a wire receiving groove formed therein andextending in a direction parallel to the prong, the disc of insulationhaving a wire receiving opening in alignment with the groove, and a wireextending through the opening and secured to the block at the groovetherein.

2. An electrical plug connecter comprising a disc of insulation, 2.block of metal having at one end a riveting stem extending through anopening in the disc and riveted over to secure the block to the disc,the opposite end of the block having a male type connecter prongextending therefrom, said block of metal having a wire receiving grooveformed therein and extending in a direction parallel to the prong, atleast a portion of the groove being exposed, a conductor extendedthrough the disc and lying in the groove and of a diameter greater thanthe depth of the groove at the exposed part, whereby the conductorextends above the edges of the groove at least at the portion of thegroove that is exposed, and means extending over the conductor at theexposed portion of the groove and clamping the conductor firmly in thegroove, said means including at least one screw-threaded member threadedinto the block of metal and efiecting the clamping action. 4

3. An electrical connecter comprising a disc of insulation, a block ofmetal having at one end a riveting stem extending through an opening inthe disc and riveted over to secure the block to the disc, the oppositeend of the block having a portion shaped to constitute one terminal of aplug and socket connecter, said block of metal having a wire receivinggroove formed therein and extending in a direction parallel to theriveting stem, the disc of insulation having a wire receiving opening inalignment with the groove,

and a wire extending through the opening and

